Buggy code:
public class CompilationUnit extends Openable implements ICompilationUnit , org . eclipse . jdt . internal . compiler . env . ICompilationUnit , SuffixConstants { public static final boolean USE_LOCAL_ELEMENTS = true ; public WorkingCopyOwner owner ; protected CompilationUnit ( PackageFragment parent , String name , WorkingCopyOwner owner ) { } public void accept ( IAbstractSyntaxTreeVisitor visitor ) throws JavaModelException { } public void becomeWorkingCopy ( IProblemRequestor problemRequestor , IProgressMonitor monitor ) throws JavaModelException { } protected boolean buildStructure ( OpenableElementInfo info , final IProgressMonitor pm , Map newElements , IResource underlyingResource ) throws JavaModelException { } public boolean canBeRemovedFromCache ( ) { } public boolean canBufferBeRemovedFromCache ( IBuffer buffer ) { } public void close ( ) throws JavaModelException { } protected void closing ( Object info ) { } public void codeComplete ( int offset , ICompletionRequestor requestor ) throws JavaModelException { } public void codeComplete ( int offset , ICompletionRequestor requestor , WorkingCopyOwner workingCopyOwner ) throws JavaModelException { } public void codeComplete ( int offset , final ICodeCompletionRequestor requestor ) throws JavaModelException { } public IJavaElement [ ] codeSelect ( int offset , int length ) throws JavaModelException { } public IJavaElement [ ] codeSelect ( int offset , int length , WorkingCopyOwner workingCopyOwner ) throws JavaModelException { } public void commit ( boolean force , IProgressMonitor monitor ) throws JavaModelException { } public void commitWorkingCopy ( boolean force , IProgressMonitor monitor ) throws JavaModelException { } public void copy ( IJavaElement container , IJavaElement sibling , String rename , boolean force , IProgressMonitor monitor ) throws JavaModelException { } protected Object createElementInfo ( ) { } public IImportDeclaration createImport ( String name , IJavaElement sibling , IProgressMonitor monitor ) throws JavaModelException { } public IPackageDeclaration createPackageDeclaration ( String name , IProgressMonitor monitor ) throws JavaModelException { } public IType createType ( String content , IJavaElement sibling , boolean force , IProgressMonitor monitor ) throws JavaModelException { } public void delete ( boolean force , IProgressMonitor monitor ) throws JavaModelException { } public void destroy ( ) { } public void discardWorkingCopy ( ) throws JavaModelException { } public boolean equals ( Object obj ) { } protected boolean equalsDOMNode ( IDOMNode node ) { } public boolean exists ( ) { } public IJavaElement [ ] findElements ( IJavaElement element ) { } public IType findPrimaryType ( ) { } public IJavaElement findSharedWorkingCopy ( IBufferFactory factory ) { } public IType [ ] getAllTypes ( ) throws JavaModelException { } public ICompilationUnit getCompilationUnit ( ) { } public char [ ] getContents ( ) { } public IResource getCorrespondingResource ( ) throws JavaModelException { } public IJavaElement getElementAt ( int position ) throws JavaModelException { } public int getElementType ( ) { } public char [ ] getFileName ( ) { } public IJavaElement getHandleFromMemento ( String token , StringTokenizer memento , WorkingCopyOwner workingCopyOwner ) { } protected char getHandleMementoDelimiter ( ) { } public IImportDeclaration getImport ( String name ) { } public IImportContainer getImportContainer ( ) { } public IImportDeclaration [ ] getImports ( ) throws JavaModelException { } public char [ ] getMainTypeName ( ) { } public IJavaElement getOriginal ( IJavaElement workingCopyElement ) { } public IJavaElement getOriginalElement ( ) { } public WorkingCopyOwner getOwner ( ) { } public IPackageDeclaration getPackageDeclaration ( String name ) { } public IPackageDeclaration [ ] getPackageDeclarations ( ) throws JavaModelException { } public char [ ] [ ] getPackageName ( ) { } public IPath getPath ( ) { } public JavaModelManager . PerWorkingCopyInfo getPerWorkingCopyInfo ( ) { } public ICompilationUnit getPrimary ( ) { } public IJavaElement getPrimaryElement ( boolean checkOwner ) { } public IResource getResource ( ) { } public String getSource ( ) throws JavaModelException { } public ISourceRange getSourceRange ( ) throws JavaModelException { } public IType getType ( String name ) { } public IType [ ] getTypes ( ) throws JavaModelException { } public IResource getUnderlyingResource ( ) throws JavaModelException { <START_BUG> if ( isWorkingCopy ( ) ) <END_BUG> return null ; return super . getUnderlyingResource ( ) ; } public IJavaElement getSharedWorkingCopy ( IProgressMonitor pm , IBufferFactory factory , IProblemRequestor problemRequestor ) throws JavaModelException { } public IJavaElement getWorkingCopy ( ) throws JavaModelException { } public ICompilationUnit getWorkingCopy ( IProgressMonitor monitor ) throws JavaModelException { } public IJavaElement getWorkingCopy ( IProgressMonitor monitor , IBufferFactory factory , IProblemRequestor problemRequestor ) throws JavaModelException { } public ICompilationUnit getWorkingCopy ( WorkingCopyOwner workingCopyOwner , IProblemRequestor problemRequestor , IProgressMonitor monitor ) throws JavaModelException { } protected boolean hasBuffer ( ) { } public boolean hasChildren ( ) throws JavaModelException { } public boolean isBasedOn ( IResource resource ) { } public boolean isConsistent ( ) { } public boolean isOpen ( ) { } public boolean isPrimary ( ) { } protected boolean isSourceElement ( ) { } protected boolean isValidCompilationUnit ( ) { } public boolean isWorkingCopy ( ) { } public void makeConsistent ( IProgressMonitor monitor ) throws JavaModelException { } public void move ( IJavaElement container , IJavaElement sibling , String rename , boolean force , IProgressMonitor monitor ) throws JavaModelException { } protected IBuffer openBuffer ( IProgressMonitor pm , Object info ) throws JavaModelException { } protected void openParent ( Object childInfo , HashMap newElements , IProgressMonitor pm ) throws JavaModelException { } public IMarker [ ] reconcile ( ) throws JavaModelException { } public void reconcile ( boolean forceProblemDetection , IProgressMonitor monitor ) throws JavaModelException { } public void reconcile ( boolean forceProblemDetection , WorkingCopyOwner workingCopyOwner , IProgressMonitor monitor ) throws JavaModelException { } public void rename ( String name , boolean force , IProgressMonitor monitor ) throws JavaModelException { } public void restore ( ) throws JavaModelException { } public void save ( IProgressMonitor pm , boolean force ) throws JavaModelException { } protected void toStringInfo ( int tab , StringBuffer buffer , Object info ) { } protected void updateTimeStamp ( CompilationUnit original ) throws JavaModelException { } }

Fix:
if ( ( isWorkingCopy ( ) ) && ( ! ( isPrimary ( ) ) ) )